The present invention relates to improvements in apparatus for attaching flexible strips or sheets to each other by means of uniting bands, and more particularly to improvements in apparatus which are especially suited for the splicing of trailing and leading ends of successive photographic films end-to-end in a photographic processing laboratory. Still more particularly, the invention relates to improvements in splicing apparatus of the type wherein the leading end of the next-following strip is attached to the trailing end of the preceding strip by a uniting band which is severed from a ribbon or tape and is caused to adhere to the strips due to the presence of an adhesive and/or under the action of heat.
Automatic or semiautomatic manipulation of photographic films in processing laboratories necessitates the conversion of a large number of successive discrete customer films into an elongated web which is convoluted onto the core of a takeup reel and is transferred into the developing machine. The developed web is thereupon caused to pass through a copying machine which makes prints of all or selected film frames before the web is subdivided into discrete films or sections of films which are assembled with associated prints and placed into envelopes for delivery or shipment to dealers or customers. The conversion of discrete films into a relatively long web (which normally consists of more than one-hundred films) brings about substantial savings in time for processing of the films. However, proper processing of a web requires the making of satisfactory splices between successive films in order to avoid breakage of the web during transport through the developing or copying machine. Moreover, the splicing operation must be carried out automatically and within short intervals of time. In many instances, the splicing operation involves the use of uniting bands which are bonded to the adjacent ends of two films, preferably in the presence of heat.
A splicing apparatus which connects successive films to each other end-to-end by resorting to uniting bands which are applied to the presence of heat is disclosed in U.S. Pat. No. 3,634,171. The uniting bands are fed to the splicing station by moving them in an elongated guide rail. The trailing end of the preceding film (which constitutes the last film of a web) is already located at the splicing station, and the splicing operation can begin as soon as the leading end of the next-following film is moved to an optimum position with respect to the trailing end of the preceding film. The next following film is a discrete film which has been withdrawn from a cassette and has been introduced into a suitable channel for transport toward the splicing station. The splicing apparatus includes a heatable ram which is mounted at a level above the splicing station and is moved downwardly to press the foremost uniting band against the adjacent ends of the films. The temperature of the ram suffices to insure melting of the adhesive layer (e.g., a hotmelt) at the underside of the uniting band which overlies the films at the splicing station. The uniting bands are obtained by withdrawing a tape from a reel and severing it at regular intervals. The severing means includes a knife on the ram and a counterknife on a table adjacent the path of movement of the ram. Thus, the leader of the tape must be introduced into the splicing station so that it extends beyond the severing plane, and such leader is converted into a uniting band in response to descent of the ram which carries the mobile knife of the severing device. The length of the uniting band, as considered in the longitudinal direction of the tape, equals or approximates the width of a film. In order to insure proper and reproducible transport of the tape, the latter is formed with perforations and the transporting mechanism includes a sprocket wheel having teeth which enter the perforations to advance the tape toward the splicing station whenever the wheel rotates. Detent means is provided to hold the tape against movement when the wheel is idle.
A drawback of the just described conventional apparatus is that the adhesive layer on a uniting band requires prolonged heating before it assumes a condition in which it forms a strong and reliable bond between the films whose ends are located at the splicing station. Furthermore, even prolonged heating of uniting bands does not guarantee the making of reliable splices. Still further, the heated ram melts the adhesive at the leading end of the tape portion immediately behind a freshly separated uniting band so that the molten adhesive contaminates the splicing station, particularly the knives of the severing device and the channel wherein the tape is fed into the range of the heated ram. This necessitates frequent and lengthy interruptions for the purpose of cleaning with attendant losses in output. Also, and since at least some of the splices are not reliable, the web is likely to break during coiling onto the core of the takeup reel which causes additional lengthy interruptions. The likelihood of melting of adhesive on the leader of the tape is especially pronounced if the operation of the splicing apparatus is interrupted for a relatively long interval of time while the heating means for the ram remains operative.